One Stop Garden Shop

The best gardening blog

Seedling Heating Mats: The Best way to Speed up Germination

Most gardening beginners haven’t got a clue what a heating mat is and what it does. In all simplicity, heat mats do exactly what is described by their name, they heat up soil. Well, heat may be a strong word, rather, they gently increase the temperature of soil which allows germination to occur quicker, reducing the timeframe for producing seedlings.

Some sites suggest that even in colder temperatures, a sunny window or a radiator would do the same job as a heating mat. However, this depends on the level of sunshine and the time during which radiators are left on. Both are time sensitive and neither method produce consistent heat, which means there are long periods of cold.
It would be much cheaper and easier to use the consistent heat of a propagation mat, which use small amounts of energy and are consistent with the level of heat being supplied to your seeds and root cuttings.

How does a Heating Mat Work?

The primary purpose of a heating mat for seedlings is to raise soil temperature to a germination level. Majority of seeds need 70F-90F to germinate, and the rate of germination is determined by the level of temperature in that range. It is important to note that there are several seeds that may need temperatures over 80F.


How to Use a Heat Mat

It doesn’t matter what container you use for your seed, whether its celled trays or pots. The main method for using seedling heat mats is the same; simply place them under your containers once the seeds have been planted and turn on the settings. We would advise checking the starting temperature and then the warmth after 3-4 days.

The deeper your soil or the denser your container, expect the length of the warming to go up in equal measure. Some mats come with thermostats; however these cannot measure the heat inside your containers, we would advise checking the temperature with a manual soil thermometer.

If your temperature starts exceeding 95F, you may want to consider removing the mats, or adding a layer between the mat and the container – this is because seeds may overheat and produce substandard results.

The other thing to keep an eye on is your soil moisture – with increased warmth comes increased evaporation, and you may find you may have to add moisture to the soil more often if you are seeing some loss.

Do You Need a Seedling Heat Mat?

The reality is that not all home gardeners need one.

The primary benefit of a Seedling heating mat is if your grow room is colder than 72F and you are trying to germinate seeds. The secondary benefit is even if you have a room at or around 72F, you could speed up the process of germination by several days by using a heat mat.

When to remove seedlings from heat mat

As we have mentioned above, the primary use for heating mats is to speed up germination. The minute your seedlings germinate (i.e start sprouting), it is time to take them off the heat mat.

Could I use a Heat Mat on Seedlings?

We would advise against the use of a heat mat for seedlings, you should limit them for seed germination or rooting cuttings.

How hot do seedling heat mats get?

A good heat mat will generate an additional 15F worth of temperature in your soil. anything more, you are risking the seedlings. Aggressive heating mats are usually reserved for really cold climates, to get soil temperature to prime germination warmth. These mats tend to be more specialist, and need rigorous control. Your average heating mat should not need much more in the way of heat.